Full Version: Hidden line removal progress

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Hello,

Awesome feature, +1000.

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Great work Michael!!! This plus Styles to layers will be very handy!

Is the bitmap output resolution determined by screen resolution?

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Can we specify the dpi or pixel dimensions on output?

Also, is this a grayscale only output or will it reflect the style color assignments?

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@danperk
> Is the bitmap output resolution determined by screen resolution?

No, it uses a software renderer that I just wrote so it's not really connected to the screen resolution. For a perspective view it will use the same shape (the same aspect ratio) as the current view though, but can use more pixels than what's currently on the screen.


@Mike
> Can we specify the dpi or pixel dimensions on output?

I think the way this one will work is you'll be able to specify a resolution in megapixels, like tell it to use 15 megapixels and that controls the pixel density. For an ortho view it positions the bitmap to cover all the objects being processed, and for a perspective view it fits it in the same aspect ratio as the current view.


> Also, is this a grayscale only output or will it reflect the style color assignments?

It will use your style colors, it will basically look like the viewport looks but with silhouettes added.

- Michael

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Nice, Thanks!

Will this work with the AI/PDF Copy/Paste?

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@danperk,

> Will this work with the AI/PDF Copy/Paste?

Yup, I think so. I'm not sure if it's possible to do alpha channel on the background image for the old AI v8 format though...

- Michael

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hi michael

this is looking great! As i have mentioned before I am a technical illustrator so its important for me to be able to work with vector versions of the 3D assets. This is a big step forward, you're not far off the $10,000 application we use! One comment I would like to add which would make working with this output far easier. Is it possible to have two different line thicknesses depending on what kind of edge it is? As you can see from my attachment I have thick and thinned your pdf, it gives it a more 3D look and feel and is a standard in tech documentation. It would be good if the lines could be differentiated like my pdf, it doesn't matter how thick as this is easily changeable document wide in illustrator.

I'm not sure if all the hidden lines are the thin lines though, but even on the expensive software you have to decide wether to keep or delete certain thin lines. Some lines like around the ankle joints are not edges but we keep them to help the viewer visualise the form. An analogy we use id if an insect walked over the model/lines and then disappeared from view then it would be a thick line . .

As i said before this is a huge leap in my line of work, well done!

Matt

Attachments:
hidden_line2_matt.pdf

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Hi Matt, this is a good time for me to get some feedback like this.

Is it always a silhouette edge that you'd like to see as a thicker one? That meaning more specifically an edge where the surface normal of that edge is at a 90 degree angle from the viewing direction.

I'm not fully understanding the insect walking rule, can you maybe give some more description of that?


I think I'm also going to try to attempt an option of making an outer boundary that's thickened, like shown in the attached file in this previous message here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4277.14


Would a thickened outside boundary like that be useful too?

- Michael

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Hi Matt, also another question - is it important to also have the hidden lines (meaning occluded lines that are not displayed at all in the PDFs here in this thread) to be available in the output to also be used for some kinds of illustrations?

I mean like the faint dashed lines that are displayed in MoI's viewport. For modeling purposes it's good to have some access to those to be able to select them, but do you use them in your illustration work as well for some things or not really?

- Michael

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Also I was thinking for the background bitmap image to maybe shrink that down by half in width and height to get a downsampled antialiased result with a bit of blending in the border areas and also cutting down file size by a ways.

Do you guys think that would be good or is it better to just keep a finer grained but non-antialiased bitmap in there?

- Michael

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hi michael

See attached pdf for more explanation of different line styles needed. At the end of the day if you can export everything except the red dotted lines (hidden lines) and then a simple line style to differentiate the others that would be great. I tried recently export a chain done using the brilliant chain script and the silhouette command. I then exported to illustrator but it was just too cumbersome to clean up. This work would go a long way to making this process a lot more painless.

hope my sketch clarifies things

Another thing on this subject, when exporting to eps, is it possible for any circles/ellipses to have just 4 points at the major and minor axes. This would clear up a lot of points and make editing/construction easier. See bottom sketch in pdf. I suspect that this bit maybe why Isodraw can charge such a high price as we are moving from 3D objects to postscript language which is moving out of your field . .

Matt

Attachments:
lineHelp.pdf

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Hi,

This is great news, the samples are looking great!

The rendering and vector curves overlapped is something I have never seen and will be a major timesaver for my work.

When profile lines have less segments (joined curves) it's easier to edit afterward.
I imagine it must be hard to set a mechanism that works great in all situations though.

I use hidden lines from time to time in illustrations or schematics.

As mentioned, a closed shape for the main silouhette would be great.
An option for different colored lines could be enough to edit the thickness of lines in 2d vector editors (for example oulines, details and hidden.)

It might be interesting to have a special export window, like when exporting polygons.
It could have a preview and some options for including the rendering or not, lighting options, hidden lines, resolution, etc.

Or maybe a 'options' button in the export pdf file dialog window could be handy.

Marc

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Michael, thanks a lot for working on the much needed hidden line removal.

I attached a nice pdf about the two lineweight illustration principle from
http://purdy.gatech.edu/wp-content/uploads/2012/07/2_line_wt.pdf

I don't know if you can control line caps on export but this is also covered.

It doesn't hurt if the hidden lines also get exported as long as they can be easily turned on and off like on a seperate layer for example.

Attachments:
2_line_wt.pdf

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"""""""""""""""""""Also I was thinking for the background bitmap image to maybe shrink that down by half in width and height to get a downsampled antialiased result with a bit of blending in the border areas and also cutting down file size by a ways.""""""""""""""""""

I'm not sure I understand what this mean, would it be easy to post examples?

Marc

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"""""""""""I mean like the faint dashed lines that are displayed in MoI's viewport. For modeling purposes it's good to have some access to those to be able to select them, but do you use them in your illustration work as well for some things or not really?""""""""""

For me it would be nice to have access to these (as seperate object/sets as mentiond). It would allow me to easily reconstruct certain parts. Like the "six legged pod" example. If I needed more of parts of the legs that were hidden, I could use those to generate something at the proper perspective. There are some 2d techniques that can require "seperating" the parts of the charactor/object onto layers/assigments.

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Hi Michael ..

I personally like the look of objects in MoI now. I often darken the visible edge lines. On my display the hidden lines are lighter and thinner and that's great though I would like it if they could be dashed.

I would also like an alternative where the surfaces did not have any color at all so that for some illustrations it would appear simply as a line drawing.

cheers,
eric

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Hi Matt, thanks for the additional explanation.

So let me make sure I understand the insect walking rule properly. I think it's about local silhouette areas, with a silhouette spot being defined by 2 conditions (previously I accidentally only wrote about one of these conditions). The 2 conditions are:
- On a smooth surface, where the surface normal is at a 90 degree angle to the viewing direction.
- On a sharp juncture between 2 surfaces, where one surface normal points towards the viewing direction and the other points away from it.

And maybe for open surfaces (instead of solids) a third condition is a "naked" edge, meaning an edge that belongs to only one surface rather than being joined between 2 surfaces.


Would having all spots that fit that criteria sorted as "Outer edges" work properly? Or is there some way for an edge to need to be considered an "Outer edge" that does not fit under this definition?


You wrote:

> For me instead of an image a sihouette shape
> would be more advantageous. This could be done if
> you can get your outer boundary shape going :-)

You mean a closed silhouette vector path? Unfortunately I'm not very confident about getting a totally clean actually closed shape for the outer boundary, I'm just hoping to slice things up so that you would have some curves separated out on that full object outside boundary so you could have another kind of thickened shape there like the one shown in the file here: http://moi3d.com/forum/index.php?webtag=MOI&msg=4277.14


> Another thing on this subject, when exporting to eps, is it possible for any circles/ellipses
> to have just 4 points at the major and minor axes.

The complication with this is that a non-rational cubic bezier with just 4 points in it cannot make an exact circle or ellipse shape, they can only approximate it. Right now MoI does a general purpose refitting step to convert any kind of rational curve into cubic beziers and general fitting mechanisms like that will end up with more points than things built for certain kinds of shapes. It might be possible in the future to make some special cases for circles and ellipses but that's probably not going to happen during this pass of hidden line removal work.

- Michael

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Hi eric,

> I personally like the look of objects in MoI now. I often darken the visible edge lines. On my display the hidden lines are
> lighter and thinner and that's great though I would like it if they could be dashed.

Are you talking now about MoI's viewport display? Or about PDF/AI export?

For the viewport display, the hidden lines are actually supposed to be dashed currently. Does your display look different than this? :



Those "hidden lines" there are not solid:




> I would also like an alternative where the surfaces did not have any color at all so that for
> some illustrations it would appear simply as a line drawing.

You can get this currently by adjusting some lighting settings so the lighting is so bright it essentially disables shading entirely.

Check out here for a description on how to set that:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3135.3

- Michael

Image Attachments:
hidden_lines1.png  hidden_lines2.png 

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Hi Marc,

> The rendering and vector curves overlapped is something I have never seen and will be a
> major timesaver for my work.

I was hoping it would be useful for your work!


> When profile lines have less segments (joined curves) it's easier to edit afterward.
> I imagine it must be hard to set a mechanism that works great in all situations though.

Also the tricky part is maintaining accuracy, it's fairly natural for fitting mechanisms to use more points in order to make the fitted result reasonably accurate. I may be able to put in some parameters to control the accuracy level at some point but I'm not quite sure about having that done for this round of work.


> As mentioned, a closed shape for the main silouhette would be great.

Unfortunately I think that's going to be really difficult to achieve, I think the best that I'll be able to do is to have an option to just try and separate out portions of curves that are on the full object silhouette so that you will have something to work with, and if you just want to make an accented border it just having a set of curves in that area may hopefully be enough for that kind of use without it being fully closed.


> It might be interesting to have a special export window, like when exporting polygons.
> It could have a preview and some options for including the rendering or not, lighting options,
> hidden lines, resolution, etc.
>
> Or maybe a 'options' button in the export pdf file dialog window could be handy.

Yeah I haven't gotten to this UI part of it yet. I'm fairly certain that PDF export dialog will get bigger with additional options right on that dialog.

I'm not sure about doing a preview, it would be nice to have but I've got to balance that against how much time it would take to implement it, and I'm not sure if the preview is going to be really particularly useful, like I'm not sure if you'd really be using it as a basis to modify parameters or not as does happen with meshing output.

- Michael

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Hi Marc,

> > """""""""""""""""""Also I was thinking for the background bitmap image to maybe shrink that down by
> > half in width and height to get a downsampled antialiased result with a bit of blending in the border
> > areas and also cutting down file size by a ways.""""""""""""""""""

> I'm not sure I understand what this mean, would it be easy to post examples?

Basically it means whether the background bitmap should be shrunk down by half and kind of blurred somewhat as a side effect of the averaging process during the shrinking.

The sort of good part is that the blurring would give the alpha transparency around the borders of shapes to have some partially translucent spots rather than only having either fully opaque or fully transparent spots with no in between things.

The bad part is that with less resolution the pixels are larger and more noticeable when zoomed in.

Maybe to start with I won't try to do any kind of processing on the background image and just leave it up to you to do any blurring or down sampling if you want that.

- Michael

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